MEMS devices are macroscale devices including a pad that is movable in response to electrical signaling. The movable pad, such as a membrane or cantilevered conductive arm, moves in response to an electrical signal to cause an electrical or mechanical effect. A particularly useful MEMS device is the MEMS shunt switch. A MEMS shunt switch grounds a signal line in one state and permits signal flow in another state. A particular switch, the RF MEMS shunt switch is an RF (radio frequency) ohmic switch. In an RF MEMS shunt switch, application of an electrical signal causes a cantilevered conductive switch pad to ground or remove from ground state a signal line by completing or breaking ohmic contact with the signal line.
MEMS lifetimes continue to be shorter than would make their use widespread. Successes in the range of 1-3 billion “cold” switching cycles have been reported. High frequency applications are especially suited to MEMS devices, and can exceed reported switching cycles in ordinary usage. Also, there is typically a difference between “hot” and “cold” switching lifetimes. Hot switching, i.e., a switching test conducted with signals present, is a different measure of operational conditions that usually shows a shorter lifetime than cold switching tests would indicate. Both types of tests are used in the art. Comparisons between the same tests are valid. However, the hot switching tests are more representative of actual operating conditions.
A common cause of failure identified by the present inventors is the deformation and breakdown of the deflection beams used to support the movable pad. Spring force supplied by the deflection beams is necessary for the operation of the switch. The deflection beams are formed from thin material, having the thinness of the movable switch pad. A loss of resiliency or breakdown of the deflection beams causes a breakdown of the switch.